Process for producing motor fuel



Oct.' 10, 1944. R. F. MARscHNER PROCESS FOR-PRODUGING MOTOR FUEL 'Filed oct'qzs. 1939 Patented Oct. 10, 1944 2,360,253 PRocEss Fon PRoDUoING Moron FUEL Robert F. Marschner, Chicago, Ill., assigner to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application October 23, 1939, Serial No. 300,734

2 claims. (ci. 26o-683.6) This invention relates to an improved process for` producing fuels for internal combustion engines. .More particularly,iit relates to an improved process for producing aviation gasoline.

Still more particularly, it relates to a process which produces both improved aviation gasoline and improved motor fuel.

In the manufacture of 100 octane number and higher aviation fuels by polymerizing the C4 cut from cracking and reforming still gases and hydrogenating the polymer, it has been found necessary to blend the isooctane and tetraethyl lead with appreciable quantities of lighter hydrocarbons in order to meet the specifications of aviation fuel. This may be accomplished by blending the isooctane with a straight-run light naphtha fraction. While this results in-the production of a fuel of the desiredspecifications, it would be preferable to employ a material for blending with the octane which would reduce its octane num-l ber to a lesser extent.

fins therein. The fraction should contain atleast from about 2% of Cs hydrocarbons up to a max. imum of 100% and preferably from about 8% to about n The desired Cs hydrocarbons may be obtained in satisfactory concentration by taking a. fraction v which distills up to about 90 F. at 1 atmosphere from a cracked or reformed hydrocarbon product from which hydrocarbons lighter than C4 have been separated. This fraction may or may not include the C4 hydrocarbons as desired. The lnvention, moreover, is not limited to the above described source for the C5 hydrocarbon fraction but includes fractions from other sources which have the same composition as the fraction described above. It is preferred, however, that, the

It is, therefore, an object of this invention to provide an improved process for producing avia- `tion fuel which involves polymerization of C4 hydrocarbons and hydrogenationof the polymers. A further object is to provide such a process in which the resulting fuel not only meets the specications for aviation fuel but, in addition, has

a higher octane'number than such fuels have heretofore had.

Another object of this invention is to produce an improved blended aviation fuel containing isooctane. Still another object is to provide a process which produces both isoootane and a hydrocarbon fraction which, whenblended with the isooctane, gives an improved aviation fuel.

These objects may be accomplished in connection with the polymerization of four carbon atom olefin hydrocarbons (hereinafter called C4 oleflnsl) and hydrogenationof the polymer to form isooctane by separating from a .hydrocarbon oil which has been subjected to treatment adapted to decrease the average molecular weight of the constituents thereof, such as cracking or rey forming treatment, a fraction containing substantial amounts of five carbon atom olefin hydrocarbons (hereinafter called "C5 oleiins), which fraction is largely free of hydrocarbons lighter than C4, and in which fraction Cs hydrocarbonsboiling below about 90 F. at atmospheric pressure predominate over those of higher boiling point to a substantially greater extent than in the aforesaid treated hydrocarbon oil and then treating-the C5 hydrocarbons included in said fraction to decrease the concentration of Ca olefraction be obtained from the same source from which the C4 hydrocarbons which are to be polymerized to isooctane are obtained. An advantageous feature of these C5 hydrocarbon containing fractions is that iso Cs hydrocarbons are a predominant constituent. On the other hand, the percentage of olens is higher than ls permitted in hydrocarbons used for blending with isooctane if' the resulting aviation fuel is to meet present specifications, so that it is necessary to subject the C5 hydrocarbons to a further treatment as disclosed above in which at least a portion of the C5 olens is eliminated. This may be accom plished, for example, by hydrogenating the Cc olens to pentanes.

A convenient and preferred method for adeeting this hydrogenation is to send the C5 hydrocarbons into a hydrogenator along with the polyf merized C4 hydrocarbons so that both are hydro genated in one operation although the invention is not limited to this feature. If the desired Cs 'to be eliminated by hydrogenation the Cs hydrocarbons are separated from the C4 hydrocarbons before the latter are sent to the polymerizer and are then added to the polymers,A passing to the hydrogenator as were the Ca hydrocarbons taken as a separate cut originally.

By taking a cut of Cs hydrocarbons not above about 90'? F. or equivalent temperatures, the fraction obtained predominates in iso Cs hydrocarbons as pointed out. Accordingly. it will have a much higher octane number than would a straight-run light naphtha fraction, for example. Thus, when it is used in place of light naphtha aviation fuel.-

to produce aviation gasoline with isooctane, the

vresulting blend will have a substantially higher knock-rating than when light naphtha from crude is used. Moreover, this will be true after either hydrogenation or polymerization or both because'of the predominance of iso C5 hydrocarbons. In addition when a substantial portion of the Cs hydrocarbons are derivedfrom a'hydrocarbon oil which has been catalytically cracked the iso C5 olefins will predominate to a greater than average extent so that the predominating product of hydrogenation is an -isopentane and thus the octane number is not materially reduced by this treatment as would be the case were a larger quantity of normal pentenes present in the cut.

Another way of eliminating the Cs olefins is to subject them to conditions bywhich they are selective polymerization and results in the production of both octenes and nonenes as well as some higher olefins. By selective polymerization is meant a catalytic polymerization under conditions to produce highly branched olefins which conditions are usually at a selected temperature in the range of 300 F. to 600 F., preferably 300 F. to 400 F., and at a pressure sufficiently high to maintain the major portion of the reactants in the liquid or dense phase. The

V`Yunreacted C5 hydrocarbons are then preferablypassed tc a hydrogenator along with the octenes whereby any pentenes present are converted to pentanes although they may be hydrogenated separately from the octenes or if the concentration of pentenes is sufficiently lowso that such a quantity of pentenes will not be undesirablerin the resulting aviation gasoline, the (3a-'hydrocarbons may be separated from the otherl materials passing out of the polymerization zone and sent directly for blending' with thejisooctane gbtagingi,

from the ,hydrogenation step to formtle desired If au the hydrocarbons higher than c5 which V774are in the effluent from the polymerizer are sent u tothe hydrogenator, the iso 09+ portion of the product having a .slightly lower octane number than theY isoo'ctanes makes the manufacture of 100+v octa''em'mb fuelsiby addition of lead more difficult.

Moreover, the Cs-ihydrocarbons raise the 50% boiling point above speciiicatidns.` 60* cheap regular motor fuels'is, however'fvery Yin.-

efiicient.

It is known from road tests that a motor fuel with a high sensitivity in the heavy ends is very desirable. By high sensitivity as usedherein,

isieat high sensitivity with respect to motor octane number-research octane number relationshlp. Thus a highly sensitive material is one which shows a large difference' in octane number depending upon whether the octane number is '75 cracked or reformed. It will be observed that ifz Thus the cut taken as dis-l determined by the motor method or by the research method. Thermally reformed naphtha in particular suffers in the respect in question because its heavy ends being largely unreformed, heavy virgin naphthas show a low sensitivity as well as a low octane number. If the Cs-ihydrocarbons present in the products obtained from the polymerizer'are separated a fraction is obtained which, because of its substantially 100% olefin content, is a highly sensitive fuel. Moreover, in concentrations below 25% these 83 to 87 octane number olefins may show blending octane numbers far above 100, depending upon the character of the base stock.

A further object of this invention is then to produce a motor fuel with high sensitivity in the heavy ends. A still further ,object is to provide a process in which hydrocarbons which are undesirable by-products from the manufacture of aviation fuel are utilized to advantage in the production of high sensitivity motor fuel. Another object is to provide a process in which both improved aviation gasoline and improved motor fuel are produced. Another object is to provide a process in which hydrocarbons produced in the` manufacture of aviation `gasoline and which would otherwise be wasted are utilized to improve motor fuel. Another object is to provide a process in which a narrow cut of C5 hydrocarbons is treated in such a way that the whole content of the cut is used to advantage in the production of fuel for internal combustion engines.y Another object is to provide a process in which a narrow cut of C5 hydrocarbons is so treated that its use results in the production of both improved aviation gasoline and improved motor fuel. Other objects will 4appear hereinafter.

These further objects are accomplished by separating the C9| olefins from the products obtained by selectively polymerizing a mixture of C4 and the narrow cut of C5 hydrocarbons re- Y peatedly referred to above and then blending the 09+ olefins into a .motor fuel, such as cracked naphtha or particularly a thermally reformed naphtha motor fuel in the manner described below in place of a. portion of the heavy naphtha which would otherwise be present therein. As

described above, the C5 hydrocarbons remaining in the polymerization products may be sent to the hydrogenation step along with the other hydro- `carbonslighter/than Qaor they may be separated prior. to hydrogenation if they are not too unsaturated to be used in blending with isooctane .to make aviation fuel.

In order that vthe invention maybe better understood, reference is madetotlattacheddrawing which forms a part of the specification aidxr which is a schematic illustrationgof an apparatus suitable for carrying out the invention. It should b'e understood, however, that the invention is not limitedV to"'this particular apparatus which is shown for purposes of illustration only and not for the purpose of limiting the scope of the invention.

dReferring to the drawing, hydrocarbon oil boiling above about 250 F., for example, naphtha having a boiling range from about 250 F. to about 400 F. or gas oil having a boiling range from about 380 F. to about '150 F. is introduced through line l0 containing valvgsgl t-andellinto'/ heater I 3 wherein it is eithercracked or reformed or else heated to a suitable temperature for introduction into catalyst chamber I6 through lines I4 and l5 wherein it is either catalytically I4 and I5 and catalyst chamber I5 into line Il and through line I1 into fractionator 2|. From fractionator 2I light naphtha and lighter products are taken overhead through line 23 and heavy naphtha and gas oil are taken off respec-= tively through lines 25 and 26, any tar formed being drawn off the bottom through line 22. The gas oil drawn off through line 26 is recycled through line 39 and valve 1I to line I 0 and thence to heater i3. If the fresh lfeed entering through line l is naphtha which is being reformed either thermally or catalytically, fractionator 2l may be operated so that everything heavier than light naphtha except tar is taken off as heavy naphtha through line 25. In this case, valve 82 inline 23 will be closed.

.Whether or not gas oil is being taken 0E through line 26 it may be desirable to recycle part or al1 of the heavy naphtha taken off through line 25. The quantity of heavy naphtha recycled may be controlled by valve 1t in line 69 and valve B3 in line 25 or if gas oil is being taken off the heavy naphtha cut may be taken at a narrower temperature range so that the heavy ends of the vnaphtha which are to be recycled are taken oil in the gas oil recycle cut. Vl/'hen the process described herein is operated in the preferred manner to produce both aviation gasoline and high sensitivity motor fuel, the quantity of heavy naphtha which is recycled may vary widely. It will be determined not only by the desired boiling range ofthe motor fuel, the desired octane number and the desired sensitivity but also by the quantity of 09+ olefins being produced. In general, it may be said that at least sufficient heavy naphtha should be recycled to prevent the 50% boiling point from being raised above the desired figure by the addition of the C9+ olen polymers. Where all of the heavy naphtha is being 4cutas a single cut this may involve recycling as much as 40% of it or more, although generally 20% or less, preferably about 10%-15%, is all -that need be sent back for further treatment. l Where a gasoil cut is being taken it is preferable to include the heavy ends of the heavy naphtha in the gas oil recycle cut by taking th'heavy naphtha cut over a narrower temperature range as outlined above. Thus, the upper temperature limit of the heavy naphtha cut which is usually about 400 F. may be lowered to 320 F. or even lower although it will usually be satisfactory vto continue this heavy naphtha cut up to 340 F. `and preferably to 375-380 F. allowing only that overhead through line 23 passthrough condenser 21 and line 28 into separator 29. VUncondensible gases such as hydrogen and methane are taken od the top of separator 29 through line 30. The

liquid in separator 29 is drawn olf the bottom through pump 14 and line 3| a-portion being re turned through line 24 to the top of fractionator 2l 'as reux and the remainder passing through line 32 into stabilizer 33 having bottom heating means.

Stabilizer 33 is operated so that C3 and lighter hydrocarbons are drawn` oil as gases from the top through line 34. Liquids are drawn off ,the bottom of stabilizer 33 and pass through line 35 and valve 84 into superfractionator having bottom heating means. This fractionator is operated so that the cut taken 0E the top through line 38 is distilled off up to a temperature of about 90F. or below at atmospheric pressure; however, the

stabilizer itself willpreferably'be operated under pressure. This overhead cut will then consist of the C4 hydrocarbons and the desired C5 hydrocarbons. Higher boiling material is withdrawn from the bottom of superfractionator 36 as light naphtha. This light naphtha passes through valve 98 and lines 3l and 58 into line 25 where it is blended with heavy naphtha and other hydrocarbons to be described later toform motor fuel. If desired, the supply of C4 andk C5 hydro carbons passing to superfractionator 35 may be augmented by supplying C4 and C5 hydrocarbons from other sources; particularly from catalytic cracking, with or without heavierhydrocarbons boiling within the boiling range of light naphtha through line 39 and valve l0 or, if an adequate supply of such a feed is available it may constitute the sole feed to superfractionator 36 in which case valve Bil will be closed.

The C4 and C5 hydrocarbons taken overhead from superfractionator 35 through line 3 8 may be passed through valve ft2` and line il into fractionator 56 by closing valve i3 and opening valves l2 and l5 or they may be by-passed around fractionator l5 by closing valves d2 and l5 and opening valve d3. When the C4 and Cs hydrocarbons are passed through fractionator te a separation between the C4 and C5 hydrocarbons is l effected therein, the c4 hydrocarbons being drawn 13 from which they are passed, by line Il into the fractionator 2| and thereafter cut as described above. Such cracked products from line 12, may Vconstitute the sole feed to thel system or may be in additionto cracked products coming from heater I3 or ,catalyst chamber I6.

` The klight naphthaand lighter products taken` Ahaving a reboiler.

off the top through line d3 and valve 45 and the C5 hydrocarbons being drawn off the bottom through line dl.

lf fractionator d@ has not been used, the' C4 and C5 hydrocarbons pass through line 3d into polymerizer d8 wherein the unsaturated hydrocarbons are selectively polymerized. The polymers and unreacted materials leave polymerizer at through line t9 and pass into debutanizer 89 Butanes leave debutanizer 50 through valve tl and line 5I from which they are introduced into line 58 and'thence into line `2E where they are blended with the light and heavy naphtha separated asv hereinbefore described to form motor fuel. If only the C4 hy- 52 and pass with the polymers into hydrogenator 82 Hydrogen is introduced intohydrogenator 82 through line 6I and unreacted hydrogen and the `hydrogenated mixture of Cs hydrocarbons and polymers are drawn from hydrogenator G2 through line 83. This mixture passes through line 63 into separator 65 wherein excess hydrogen is separated and drawn off through line 8d and valve 10|. The liquids in separator 65 are then drawn-od through line Sii and valve idil as' finished aviation gasoline.

When both aviation gasoline and motor fuel of high sensitivity are being made instead of separating the C5 hydrocarbons frontl the .C4 hydrocarbons in fractionator it the mixture leaving superfractionator d@ passes through line 38 and valve '33 directly into polymerizer 4B, valves d2 and i5 in this instance being closed. After being selectively polymerized in polymerizer 48 the mixture passes through line 89 into debutanizer 50 as described above when only the Cis were passed to the polymerizer. Debutanizer 5i) is 'also operated in the Way which has already been described so that only the Ci hydrocarbons are taken out through line 5i. The remainder of the charge leaves debutanizer do through line 52 as before but this time valves 55 and 56 are closed and valves 54 and S@ are open so that the materials pass through line 52 into line 53 and through valve 54 into fractionator d?. Fractonator 5l is so operated that the C9 and higher oleflns are taken oi as a bottom product through line E8 and valve t8 and thence intoline 25 so that the motor fuel drawn ou lthrough line 25 is a blend of light naphtha, heavy naphtha, butanes and the C9 and higher oleilns derived from fractionator 57. In making such a gasoline which has a very high sensitivity a portion of the heavy naphtha Withdrawn from ractionator '2l through line 25 is recycled through line S9 and line i@ to heater iii. This portion of heavy naphtha recycled is adjusted so that it is about equal to the quantity of C9 and higher olens Withdrawn from fractonator 5? through line 58. A portion of the heavy naphtha in the gasoline Withdrawn through line 25 is thus replaced by an equivalent quantity of the Cs and higher olens.

The products leaving the top of fractlonator 5l through line 59 consist mainly of C5 and Cs hydrocarbons. They may be passed through valve 6i) to line 52 and into hydrogenator B2,

hydrogen being passed through line Si intoA hydrogenator 62 as before. In operating in this manner any C5 olefins not polymerized in polymerizer 48 are hydrogenated in hydrogenator 62 along with the isooctane so that after the products ofhydrogenation are separated from excess hydrogen in separator t5 a finished aviation gasoline is drawn bfi through line 66.

. If the hydrocarbons leaving. fractionator 57 through line 59 are suciently low in C5 oleiins so that the 'quantity will not be objectionable in aviation gasoline it is unnecessary to hydrogenate these C5 hydrocarbons and the quantity of material passing to hydrogenator 62 can thus be decreased by closing valve .60 and opening valve 15 so that the overhead from fractionator 57 passes through line 1Q rvinto depentanizer l1 having a reboiler.. TheA C5 hydrocarbons are drawn ofi the top of depentaniaer 'i1 through line accesos is separated as before and from. which they are withdrawn through line t5 wherein they are blended with the Cs hydrocarbons from line lo as pointed out above making nnished aviation gasoline of the desired characteristics.

It will thus'be seen that this process may be operated in any one o three ways each of which has, however, the common characteristic that C5 hydrocarbons boiling up to about 90 F. at atmospheric pressure are separated from other Ca and higher hydrocarbons after which these lower boiling C5 hydrocarbons are treated to decrease the concentration of Cs oleilns therein and then withdrawn from lthe system as a conm stituent of r nished aviation gasoline which has not only a high knock rating but which, in addition, has improved boiling characteristics,

It is not always convenient or practical to produce the various components of either the motor fuel or the aviation gasoline in theexact proportions desired for blending so that it is usually necessary to store one or more of these cuts or products. For this reason valved lines are pro vided for drawing oi and sending to storage (not shown) for use at other times or for other uses, the Cis from line 5l, the Css from either line il or line 78, the light naphtha from line di. the heavy naphtha from line 2d, and the Ce and. higher olens from line 553. These lines with their accompanying valves, are, respectively, line Sg and valve 90, line Q5 and valve Sd, line s3 and valve Sd, line 81 and valve dii, line d5 and valve 8b, and line Si and valve di?. No additional means for drawing ofi hydrcgenated materials separately from 05's entering line do through line 78 is shown since line SS itself can be used for this purpose when valve le is closed.

A preferred method of operation involves in-1 troducing naphtha through line ill, and either thermally reforming or thermally cracking it in heater i3, then fractionating the cracked or re- 1 formed materials in fractionator 2l s'o that light 1l, condenser H02, and valve 1 Where they are blended with the gasoline withdrawn-'from separator 65 through line 66 to give'the finished aviation gasoline withdrawn from line i6. The

'hydrocarbons higher than C5 leave the denaphtha and lighter materials are drawn off the top, so that heavy naphtha is drawn off through line 25, and so that the material heavier than heavy naphtha such as tar passes out through line 22. A portion of the heavy naphtha roughly corresponding in quantity to the quantity of Cs and higher oleins leaving fractionator 5'? through line 58 is recycled through line-SS. Separator 2S, stabilizer 33. and superfractionator 36 are all operated in the manner already described above but the feed through line 35 to superfractionator 3i is supplemented by introducing through line 3S and valve 40, a fraction of a mixture of hydra carbone obtained by catalytically cracking naphtha. gas oil or similar hydrocarbon oil and fractionating to l remove heavy naphtha and vheavier hydrocarbons as 'well as hydrocarbons lighter than C4. Such a fraction will be high in olen content as well as in content of iso C4 and iso C5 olens and parains. and C5 hydrocarbons leaving superfraetionator 26 through line 38. is, in the preferred process, by-pa'ssed around fractionator et by closing valves t5 and 87 and is sent directly to polymerizer @18. After being subjected to selective polymerization therein the hydrocarbons are debutanized in debutanizer 50 and then sent to fractionator 5l 'by having valves 55 and 56 closed and valve B open. In fractionator 51 the C9 and higher oleilns are drawn oil the bottom and are sent back to replace the heavy naphtha recycled in forming the The mixture of C4 drawn through line 25. With valves 19 8| and 'l5 closed and valve 60 open the overhead from fractionator 51 is then passed through -line 52 into hydrogenator 52 and then into separator 65 and a nmshed aviation gasoiine4 is withdrawn through line 6B. `Depending upon the relative quantitiesof each, .the various constituents of both the motor fuel and the aviation gasoline may, if desired, be sent in part or wholly to storage prior to blending to form the flnished products.

The conditions of operation to be used in connection with the various towers, furnaces, etc., shown on the accompanying ilow sheet and described above are in large part familiar to those skilled inthe art since they are conventional and, therefore, detailed conditions of operation need not in every instance bespecied. The above description of the purpose of these various pieces of equipment, is, in general, sufficient to enable anyone skilled in the art to practice the process of the invention.

Accordingly the invention is not limited as to conditions of operation so long as the conditions are such as to elect in the towers, furnaces, etc., the operations which are fully described above. Certain conditions are, however, preferred. Thus when a hydrocarbon oil is being treated thermally in heater i3 it is ,preferable that the temperature be in the 'range from about 900 F. to about 1025 F. for example 975 F. and that the pressure be about atmospheric orvabove up to about 1000 lbs., for example 2.00 lbs. Under these conditions a soaking time suicient to give about 10% to about 50% of gasoline per pass is preferred. For catalytic cracking or reforming, temperatures in the range from about 750 F., to about 950 F., for example 875 F., rates of feed such that about 0.1 to about 5 volumes of liquid oil feed are passed per hour per volume of catalyst space, for example l volume, pressures from about atmospheric to about lbs., for example 10 lbs., and

catalyst holding times of about 5 minutes to about l0 hours, for example, A30 minutes, are preferred. Preferred cracking and lreforming catalysts include absorbent earths, such as natural or synthetic clays, as well as active catalysts, such as alumina, thoria,l or zirconia hydrolytically absorbedor otherwise mounted on a siliceous support. Phosphoric acid on kieselguhr or any other known cracking or reforming catalyst may, however, be used, if desired.

As has already been indicated the polymerization described above is preferably selective In the definition-of 4selective polymerization given nin connection with the rst use of the term herein, it is stated among other things that the poly- 4rnerization is catalytic and that it is under sufdcient pressure to maintain the reactants in the liquid or dense phase. Preferred catalysts for fuels, such as low temperature processes using liquid catalysts; for example, sulfuric acid or sulfuric acid-phosphoric acid mixtures. In such processes the ow rate will depend on the activity of the catalyst and should be such that preferably from about 80% to about'l00% of the isobutylene in the charge is converted tohigher boilmercially recognized types of procedure is preferred. These types are the high pressure process, using specially composed 6th group catalysts, preferably a catalyst comprising molybdenum, and the low pressure process using nickel. Preferred conditions for the high pressure process are temperatures in the range from about 550 F. to about 850 F., for example 725 F., pressures in the range from about 250 lbs. to about 5000 lbs., for example 450 lbs., hydrogen to olefin molar ratios from about 2 to aboutQ 25, for example 8 and rates of ow of about 0.1 to about 5 volumes of liquid hydrocarbon feed/volume of catalyst space/hour, for example 0.6 volume hyd rocarbon/volume catalyst space/hour, i

For'the low pressure process the preferred operating conditions involve temperatures in the range from about 200 F. to about 500 F., for example 425 F., pressures from about 10 lbs. to about 150 lbs., f or example 35 lbs., excess of hydrogen over the theoretical of from about 3% to about 100%, for example 10%, and rates of ilow of about 1v` to about l5 volumes of liquid hydrocarbon feed/volume of catalyst space/hour, for example, 4 volumes hydrocarbon-volume of catalyst space/hour.

Byway of further facilitating a complete understanding of the present invention, the fol-A lowing example is included. It should be understood that this example is included for illustration only and, therefore, it is not intended to be construed as limiting the scope of the invention.

Example-Gas oil is about 30% thermally cracked at about 975 F. under a pressure of about 250 pounds per square inch and the product is separated into xed gas, wet gas, light naphtha (250 F.E. P.) heavy naphtha (380 F.- E.P.) ,-cycle stock and tar. It will be noted that the heavyends of the naphtha are thus included in the cycle stock. The combined wet gas and this polymerization include catalysts of the phos-l plioric acid on kieselguhr type, as Well as those o! the copper pyrophosphate type or catalysts equivalent to these types. In stating that the reactants should be under sufficient pressure to maintain them in the liquid or dense phase', it is meant that the pressure should be at least high enough so that the reactants are in that portion oi' the dense phase region'which is above the extrapolated vapor pressure curve for-the charge.

Moreover, although selective polymerization is preferred, it is Within the scope of the invention to employ other polymerization procedures which lead to the production of high octane number light naphtha is stabilized Ca-free and about 25 volumes percent of a similarly stabilized fraction from catalytic cracking isA added. This mixture is then superfractionated to about F. at one atmosphereto give a mixture overhead of about 79% C4 hydrocarbons which are about 48% unsaturated and contain about 22% isobutylene,

the rest of tlie mixture (about 21%) being Cs hydrocarbons, which are also about 48% unsaturated and contain a proportion of branched` oleiins approximating that inthe C4 hydrocarbons, the non-olefin material including relatively small amounts of n-pentane. This overhead mixture of C4 and C5 hydrocarbons is then passed over a phosphoric acid on kieselguhr catalyst 'at a. temperature of about 345"l F. under a'. pressure of about 985 pounds per square inch gage, at a i rate of about 10 volumes of liquid hydrocarbons theoretical of about 10%.

per volume of catalyst per hour by which about 95% of the branched C4 and Gs olens and about 60% of the total C4 and Cs olens are polymer= ized to liquids. ponlractionation of the prod. uct about 55% passes overhead below about 46 Fr This overhead which consists almost entirely of C4 hydrocarbons is blended in motor fuel or stored for use for this or other purposes. The portion (about 45%) of the product remaining after removal of the Ct's ls then further fractioncted. n this fractionation an overhead fraction is taken up to about 255 F. and consists of about 42% Cs (containing 19% olens) and about 53% dibutylenes. It amounts to about 30% of the total efilueht from the polymerization. The other 15%, which remains as bottoms in the latter fractionation, consists of C9 and higher (1/3 Crzs and CMH hydrocarbons.l it is then blended in a motor fuel or stored for use i'or this purpose. The overhead fraction of Cs and dibutylenes is then non-destructively hydrogenoted at atemperature of about 425 F. over a nickel catalyst under a pressure of about 35 pounds using an excess or" hydrogen over the The product is an aviation gasoline with an octane number of about 90s-92 and a vapor pressure at 100 F. of more than 6 pounds. To obtain a product of similar voiatility by blending a 67 O. N. light straight run naphtha with the commercial isooctane lowers the octane number to about 85. More over, the lead response of the S90-92 O. N. product is actually slightly higher than that of the isooctane-light naphtha blend. When the heavy naphtha fraction separated as described above having a motor octane number of about 6i is blended with the {s-@w+ bottoms described above which have a motor octane number of about 82 and'replace the portion of the heavy naphtha included in the gas oil fraction and recycled, the motor octane number of the heavy blend is :increased to about 63. r"his heavy blend and the light naphtha are combined with suffi cient of the Cts separated above to produce a balanced motor fuel which shows good sensitivity throughout its boiling range as shown by the following table:

The advantages of the present invention will be apparent from the above description. In the production of aviation gasoline by polymerization and hydrogenation o C4 hydrocarbons av method is provided for overcoming the diiculty heretofore encountered in obtaining gasoline of the desired boiling characteristics without unduly reducing the octane number at the same time.

This isaccomplished without the necessity for any additional equipment over that employed to polymerize and hydrogenate the@A hydrocarbons. Moreover, the presence of the C5 hydrocarbons during selective polymerization is, itself, f

advantageous since it helps to maintain the desired dense phase. An even more outstanding vadvantage of the process is that it is possible to produce along with the improved aviation gasoline an improved :motor fuel from reformed nacht-ha which has a desired high sensitivity in the heavy ends. Another advantage of the process when operated in accordance with the preferred method is that the Cs oleins are elirntn noted largely by polymerization thereby decrees ing the charge to the more expensive hydrogenaa tion operation.

yt is apparent that many widely different em bodiments of this invention may be made with out departing from the spirit and scope thereof and, therefore, it is not intended to be limited except as indicated in the appended claims.

claim:

l. The process `which comprises thermally cracking gas oil, fractionati'rig the resulting mixn tures into a tar fraction, a recycle fraction iu= cluding the heavy ends of heavy naphtha, e, discard traction lighter than C4, a fraction including 'the rest of the heavy riaphtha, and a light naphthe. fraction including the C4 and Cs hydro carbone,V adding to said light naphtha fraction a substantial quantity of a simila1';-iraction from. catalytic cracking,l fractionating the resulting mixture into a bottom light naphtha fraction and au overhead fraction containing the @shya drocarbons and such of the @s .hydrocarbons as are included by taking the cut up to about @0 at atmospheric pressure, recovering Vfrom said' overhead fraction a residual fraction containing substantial amounts of iso Ct hydrocarbons and a second overhead fraction, polymerizing said second overhead fraction, fractionating the products ci said polymerization into a Crfraction, an intermediate fraction inciuding C@ hydrocar= bons, and a C9 and higher traction, hydrogenating the said intermediate traction in admixture with the recovered isc @fi-hydrocarbons to satuu rate the compounds therein with hydrogen and produce an aviation fuel of goed boiling range, blending said fraction containing the rest of the heavy naphtha, said bottom light naphtha fracm tion, said C9 and higher fraction and enough of said C4 fraction from the polymerization step to produce a balanced motor fuel of high sensia tivity throughs s .boiling range.

2. The process 1 `claim l further charac y'zerized iu that the polymerization is carried out at a temrature in the range of about 300 F. Ito about A200 if'. and in thepresenceof asolid selective polymerization catalyst.

HUBERT ii. MARSCHNER. j 

